I’m kinda bad at explaining but I’ll toss some more names (as well as reiterating suggestions for FMA03, Mushishi and Planetes, all 3 great shows):
-Gankutsuou: Sci-Fi reimagining of the Count of Monte Cristo. It has some weird choices but it’s overall really good.
-Kaiji: an indebted guy does gambling to try to solve his problems. Lots of mind games and suspense, way better than what it sounds like. One of my personal favorites.
-Higurashi no Naku Koro Ni: Horror/Mystery series set in a secluded village. It has some clichès and the animation… isn’t the best, but I really liked it personally. Don’t bother with the third and fourth seasons that came out recently (or do, but they’re honestly not needed at all).
-Monster: Thriller about an ex-Surgeon trying to find a past patient turned murderer. From Urasawa, if you know the name.
-Paranoia Agent: Mystery semi-episodic series about a lot of different characters, their life struggles and a mysterious boy going around beating people with a golden bat for no apparent reason. From Satoshi Kon (his movies are all really good too btw).